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2011-02-14_PERMIT FILE - C1980007A (3)
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2011-02-14_PERMIT FILE - C1980007A (3)
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Last modified
12/13/2018 7:01:03 AM
Creation date
4/14/2011 9:10:05 AM
Metadata
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Template:
DRMS Permit Index
Permit No
C1980007A
IBM Index Class Name
Permit File
Doc Date
2/14/2011
Doc Name
SUBSIDENCE EVALUATION
Section_Exhibit Name
Exhibit 60E Subsidence Evaluation for the South of Divide and Dry Fork Mining Areas
Media Type
D
Archive
Yes
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Subsidence Evaluation for the <br />Exhibit 60E South of Divide and Dry Fork Mining Areas Page 35 <br />11.4.2 Water- Bearing Zones <br />Horizontal strain produced during subsidence could impact local water - bearing zones in bedrock <br />beneath the blanket of clay -rich surficial material. It also may impact local water - bearing zones <br />in surficial material, where permeable and saturated zones are stratigraphically positioned in <br />zones of tensile strain. Impacts may occur for long periods of time, where the water -bearing <br />zone is located above mine boundaries and barrier pillars, areas where permanent strain occurs. <br />On the other hand, dynamic strains and related cracks produced by subsidence above moving <br />longwall faces in a given area are nil and close when the longwall faces move out of the area of <br />influence of this area. Based on Dunrud's evaluation, any mining effects on local on water - <br />bearing zones can best be identified by monitoring any changes in flow and water levels in <br />springs and ground water wells (as discussed in Section 11.4.3). <br />11.4.3 Ground Water Wells <br />The two monitored, ground water wells (23 -H -1 and 23 -H -2) in the South of Divide mining area <br />are located east of and near the mouth of Deer Creek. They are located above, or within the <br />areas of mining influence of the barrier pillar areas and haulageways of projected E -seam <br />longwall panels E2 and E3. Overburden depth to the E -seam is approximately 375 to 400 feet. <br />The major source of the water in these is wells likely from colluvium and alluvium in the Deer <br />Creek drainage. There are also two groundwater monitoring wells in the Dry Fork mining area. <br />A shallow well in the upper Dry Fork was reportedly installed in 2003 but is no longer monitored <br />and its status is unknown. (U.S. Dept. of Agriculture. 2005). A groundwater monitoring well (96- <br />2 -2) was completed to bedrock by the West Elk Mine is monitored three times a year. This <br />groundwater monitoring well is located over the potentially extended eastern end of E -seam <br />longwall panel E3. <br />These wells, and any other water wells within the area of mining influence should be monitored <br />for as many years prior to mining as possible, in order to determine baseline information that <br />would yield seasonal variations. <br />11.5 Roads <br />Based on past observations in the Apache Rocks and Box Canyon mining areas, effects from <br />mine subsidence are expected to be limited to cracks that would not prevent passage on most of <br />the access roads and drill roads in the South of Divide and Dry Fork mining areas. Also, no <br />effects from landslide movements or rockfalls are expected, because the mining rockfall <br />potential is mapped in the moderate -high category or lower, and rockfalls were observed to occur <br />only in the high to very high rockfall category areas in the Box Canyon mining area. <br />Although no cracks are expected in the soft, pliable alluvium, some cracks are expected to occur <br />on the harder and more highly compacted Dry Fork access road, particularly in the area near the <br />confluence of Deer Creek and Dry Fork. As discussed previously, the range of maximum <br />vertical displacement, tilt, and horizontal strain is projected to be 8.4 to 11.2 feet, 1.3 to 6.4 <br />percent, and 0.7 to 4.2 percent (respectively) in the Dry Fork stream valley and road above the <br />solid coal boundaries at the western limits of E -seam longwall panels E2 and E3. <br />• <br />831 - 032.810 Wright Water Engineers, Inc. <br />
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